I know nothing about this except it seems fun. I've heard of people spearing makos and trying to get them in. Can anyone tell me about spearfishing for sharks?

Do you spearfish already?
If not, I would not start with sharks lol.

Most of the time, when you are going to shoot a shark, or anything big, you need a float line. That way, you shoot and you are completely free from your shaft/the fish. Have enough of a float on the end of the line that it either won't go down or wont stay down long. Swim up, reload your gun with another shaft/float line, and start pullng him in. If it is a big fish or it might pull out, then swim down there and get another shot. 2nd shot should be a kill shot, ie gills or spine. Then pull them up and watch out for the teeth.

I haven't shot a shark, but best way to get them to come around you is to go shoot a bunch of other fish while you wait for them to come find you. Go smack a couple on a rig and swim out and they will try to steal them before you hit the boat(bulls, spinners, blacktip, bonnets, hammers, seen them all at rigs) Only mako ive swam with was on a rip about 40 miles out. We were shooting dolphins and a 4fter came swimming up. We werent set up for a fight like that so we just got out of the water.

Big sharks will not enter a rig, but they will see how fast they can swim in a circle around it.

In Texas, sharks can be taken by rod and reel only.